Bioactive spinal implants and method of manufacture thereof

ABSTRACT

A bioactive spinal implant used in cervical fusion, Anterior Lumbar Interbody Fusion (ALIF), Posterior Lumbar Interbody Fusion (PLIF), and Transforaminal Interbody Fusion (TLIF), having properties and geometries that enhance bone contact, stability, and fusion between adjacent vertebral bodies.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. application Ser. No.14/244,354, filed Apr. 3, 2014, which is a divisional of U.S.application Ser. No. 11/736,314, filed Apr. 17, 2007 and now U.S. Pat.No. 8,715,353, which is a divisional of U.S. application Ser. No.10/256,566, filed Sep. 26, 2002 and now U.S. Pat. No. 7,238,203, whichclaims priority to U.S. Provisional Application No. 60/339,871, filed onDec. 12, 2001, the contents of which are incorporated herein byreference in their entireties.

FIELD OF THE INVENTION

This present invention generally relates to spinal fixation devices, andspinal implants, suitable for use in orthopedic applications in whichthe implant is subjected to dynamic, compressive loads. The implants ofthe present invention may be used in procedures such as cervical fusion,Anterior Lumbar Interbody Fusion (ALIF), Posterior Lumbar InterbodyFusion (PLIF), and Transforaminal Lumbar Interbody Fusion (TLIF). Theymay be implanted between adjacent vertebrae to treat or prevent backpain in patients with conditions such as degenerative disc disease. Thepresent invention also relates to methods of making bioactive implantsand apparatuses for manipulating them.

BACKGROUND OF THE INVENTION

Lower back and neck pain is oftentimes attributed to the rupture ordegeneration of intervertebral discs due to degenerative disk disease,spondylolisthesis, deformative disorders, trauma, tumors and the like.This pain typically results from the compression of spinal nerve rootsby damaged discs between the vertebra, the collapse of the disc, or theresulting adverse effects of bearing the patient's body weight through adamaged, unstable vertebral structure. To remedy this, spinal implantshave been inserted between vertebral bodies to restore the structure toits previous height and conformation and stabilize motion at that spinalsegment.

Surgical treatments to restore vertebral height typically involveexcision of the ruptured soft disc between two vertebrae, usually withsubsequent insertion of a spinal implant or interbody fusion device tofuse and stabilize the segment. Spinal implants or interbody fusiondevices have been used to fuse adjacent vertebral bodies since the1960's. Currently, spinal implant devices are comprised of eitherallograft materials, natural, porous materials such as coral, orsynthetic materials. A major drawback associated with allograft devicesis the risk of disease transmission. Further, since companies thatprovide allograft implants obtain their supply from donor tissue banks,there tend to be limitations on supply. Synthetic devices, which arepredominantly comprised of metals, such as titanium, also presentdrawbacks. For instance, the appearance of metal spinal implants onx-ray tends to have an artificial fuzziness, which makes assessment offusion (one of the clinical criteria of a successful interbody fusiondevice) very difficult. Moreover, synthetic materials of this type(metals) tend to have mechanical properties that are unevenly matched tobone. Coral and other natural materials generally perform poorly.

Accordingly, there is a need in the art for a synthetic spinal implantmaterial that does not carry the risk of disease transmission as withallograft materials.

There is also a need for a synthetic spinal implant material with aradiopacity similar to bone. A radiopacity similar to bone would allowfor visualization of the implant between the vertebrae to assessradiographic fusion without distortion.

Further, there is a need for implants with mechanical properties similarto that of bone that can share the physiologic, dynamic compressiveloads rather than shield them.

Moreover, there is a need for implants that are comprised of a materialthat bonds directly to bone and is bioactive.

In addition to the material limitations associated with existingimplants on the market, there is also a need to provide spinal implantsthat are anatomically shaped with proper geometry and features toprevent expulsion or retropulsion. The term “expulsion” as used hereinrelates to the migration of the implant device in a forward (orbackward) direction from the intervertebral space. Moreover, there is aneed for a device with an increased surface area to allow for optimalcontact with the cortical bone to prevent subsidence or sinking of theimplant into each adjacent vertebra. There is a need to provide animplant that is bioactive with an open geometry for packing with graftmaterials that allows enhanced fusion between the endplates of adjacentvertebrae both via the bioactive surface of the implant and a preferredgraft-packed opening.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be more clearly understood when considered inconjunction with the drawing figures, wherein:

FIG. 1 provides an isometric view of one embodiment of a cervicalimplant 10.

FIG. 2 provides a front view illustrating the anterior side of thecervical implant 10.

FIG. 3 provides a side view illustrating the medial side of the cervicalimplant 10.

FIGS. 3 a and 3 b provide side views illustrating the cervical implant10 with and without a lordotic angle, respectively.

FIG. 4 provides a planar view illustrating the substantially trapezoidalshape of the top and bottom surfaces of the cervical implant 10.

FIG. 5 provides an exploded view of the cervical implant 10 with asynthetic graft material.

FIG. 6 provides an isometric view of a cervical plate and fastenerassembly 100.

FIG. 7 provides an isometric view of the cervical implant 10 with acervical plate and fastener assembly 100.

FIG. 8 provides another view of the cervical implant 10 with thecervical plate and fastener assembly 100.

FIG. 9 provides an isometric view of an embodiment of a connectoraccessory 110 that may be used in connection with the cervical implant10.

FIG. 10 provides an isometric view of another embodiment of a spaceraccessory 120 that may be used in connection with the cervical implant10.

FIG. 11 provides an isometric view of the connector accessory 110 andthe spacer accessory 120 that may be used to mate two cervical implants10.

FIG. 12 provides an isometric view of one embodiment of the ALIF implant130.

FIG. 13 provides a front view illustrating the anterior side of the ALIFimplant

FIG. 14 provides a side view illustrating the medial side or lateralside of the ALIF implant 130.

FIG. 15 provides an isometric view of an alternate embodiment of theALIF implant 200.

FIG. 16 provides an isometric view of the ALIF implant 200 that includesa fastening feature.

FIG. 17 provides a front view of the ALIF implant 200 and a fasteningfeature.

FIG. 18 provides a side view of the ALIF implant 200 and a fasteningfeature.

FIG. 19 provides a cross-sectional view of the ALIF implant 200 and afastening feature.

FIG. 20 provides an isometric view of one embodiment of the PLIF implant240.

FIG. 21 provides an isometric, side view of another embodiment of thePLIF implant 240.

FIG. 22 provides an isometric view of yet another embodiment of the PLIFimplant 240.

FIG. 22A provides an isometric view of one embodiment of a TLIF implantx1.

FIG. 22B provides a top and bottom planar view of implant of x1.

FIG. 22C provides an isometric view of one embodiment of a TLIF implantx1 illustrating two lateral openings.

FIG. 22D provides a planar view illustrating the openings x12 and x13and recesses on the anterior x8 and posterior xa sides of the TLIFimplant x1.

FIG. 23 provides an isometric view of one embodiment of the paralleldistraction instrument 310 engaging the ALIF implant 130.

FIG. 24 provides a side view of the parallel distraction instrument 310engaging the ALIF implant 130.

FIG. 25 provides an exploded view of the pair of upper 320 and lowerforks 330 of the parallel distraction instrument 310.

FIG. 26 provides a detailed, isometric view of the parallel distractioninstrument 310.

FIG. 27 provides an isometric view of the parallel distractioninstrument 310 illustrating the grasping end 340 or handle of theinstrument.

FIG. 28 provides an isometric view of one embodiment of the implantinsertion tool 350.

FIG. 29 provides a detailed view of the tip of the implant insertiontool 350.

FIG. 30 provides an isometric view of another embodiment of the implantinsertion tool 350 featuring a threaded tip.

FIG. 31 provides a detailed, isometric view of the implant insertiontool 350 about to engage the ALIF implant 130.

FIG. 32 provides an isometric view of the implant insertion tool 390prior to engaging cervical implant 10.

FIG. 33 provides an isometric view of the implant insertion tool 390engaging cervical implant.

FIG. 34 provides a side view of the implant insertion tool 390 insertingcervical implant 10 between two vertebral bodies.

FIG. 35 provides a side view of another embodiment of the implantinsertion tool 110 inserting the cervical implant 10 between twovertebral bodies.

FIG. 36 provides a planar view of one embodiment of forceps 440.

FIG. 37 provides a detailed, planar view of the forceps 440 engagingcervical implant 10.

FIG. 38 provides an isometric view of the forceps 440 engaging thecervical implant 10.

FIG. 39 provides a detailed, isometric view of the forceps 440 engagingthe cervical implant 10.

FIG. 40 provides an exploded, isometric view of one embodiment of theinsertion tool 470 of the present invention.

FIG. 41 provides an isometric view of the assembled insertion tool 470.

FIG. 42 provides an isometric view of another embodiment of theinsertion tool 500.

FIG. 43 provides a detailed isometric view of an embodiment of theinsertion tool 500 of the present invention engaging the cervicalimplant 10.

FIG. 44 provides an isometric view of the insertion tool 00 and oneembodiment of the impactor hammer 510 of the present invention.

FIG. 45 provides an isometric view of the insertion tool 500 and thecervical implant 10 being inserted between two vertebral bodies.

FIG. 46 provides a side view of the insertion tool 500 and the cervicalimplant 10 being inserted between two vertebral bodies.

FIGS. 47 a through 47 c provide a front view of the insertion tool 500being used to adjust the position of the implant 10 between the twovertebral bodies.

FIG. 47D provides a side view illustrating a rasp instrument y1 of thepresent invention to be used to shape the endplate prior to implantinsertion.

FIG. 48 provides isometric views of one embodiment of trial implanttools of the present invention.

FIG. 49 provides a detailed, isometric view of the trial implant of FIG.48.

FIG. 50 provides an isometric view of one embodiment of the graftimpaction block 540 of the present invention.

FIG. 51 provides an isometric view of the graft impaction block 540 andthe forceps tool 440 engaging the cervical implant 10.

FIG. 52 provides an isometric view of the graft impaction block 540 andthe inseltion of graft material into the cervical implant 10.

FIG. 53 a provides a radiograph of an implant of the present inventionafter insertion between adjacent vertebrae in a sheep spine, and FIGS.53 b and 53 c provide a radiograph and corresponding image,respectively, of a present invention implant (top) in comparison to atitanium implant (bottom) in a calf spine.

FIG. 54 provides Fourier Transform Infrared Spectroscopy (FTIR) spectrumof the material of the present invention at Day 0, 6, 19 and 50 incomparison to hydroxyapatite.

FIG. 55 provides back-scattered electron (BSE) microscopy images of thematerial of the present invention at Day 0.

FIG. 56 provides (a) a Scanning Electron Microscopy (SEM) image of a Day6 sample of the material of the present invention with a layer ofcalcium phosphate on the surface of a bioactive filler (2500X), (b) SEMof a cross-section of Day 19 with a CaP growth on the surface of abioactive filler (2500X).

FIG. 57 provides (a) a SEM of a Day 50 sample of the material of thepresent invention with a layer of CaP on its surface (250X), (b) SEM ofa Day 50 sample of the material of the present invention with a thick,dense, needlelike growth of CaP on its surface (1000X) (c) SEM of across-section of a Day 50 sample of the material of the presentinvention, CaP has covered the surface and grown into the bioactivefiller (1500X).

FIGS. 58 a, b, c provide implants of the present invention with basic orwave-like tooth profile, pyramid tooth profile, and oblique toothprofile, respectively.

FIG. 59 provides a cat-scan (CT) image of the implant of the presentinvention implanted in a non-human primate model.

FIG. 60 provides a cat-scan (CT) image of the implant of the presentinvention implanted in a non-human primate model.

SUMMARY OF THE INVENTION

The present invention provides spinal implants that have a radiopacitysimilar to bone for facilitating radiographic assessment of fusion. Thepresent invention also provides spinal implants having properties andgeometries that enhance bone contact, stability and fusion betweenadjacent vertebral bodies. The implants of the present invention arecomprised of bioactive and biocompatible materials capable ofwithstanding physiologic dynamic, compressive loads. As used herein,bioactive relates to the chemical formation of a calcium phosphatelayer, such as, via ion exchange between surrounding fluid and theimplant material. More broadly, it also relates to a material thatelicits a reaction which leads to bone formation or attachment into oradjacent to the implant, for example, bone formation or appositiondirectly to the implant usually without intervening fibrous tissue.Biocompatible as used herein relates to a material that does not invokea prolonged, adverse immunologic or host response.

The present invention also provides methods for making such implants andinstrumentation for inserting same. In one embodiment of the presentinvention, there is provided a spinal implant comprised of a top and abottom surface having a substantially trapezoidal cross-section, aplurality of wave-like protrusions, and at least one opening. The topand bottom surface are preferably substantially convex with respect toeach other; and have a pair of medial and lateral sides that extendbetween the top and bottom surfaces. The medial and lateral sidespreferably have at least one indentation and at least one opening. Apair of anterior and posterior sides preferably extends between the topand bottom surfaces and contacts at least a portion of the pair ofmedial and lateral sides. The anterior or posterior sides alsopreferably have at least one opening.

In another embodiment of the present invention the implant has agenerally trapezoidal, ring-shaped body with bowed sides and convexsuperior and inferior surfaces. Such configuration is particularlysuitable for use in orthopedic applications, such as in the spine, as aspinal implant. The implant is anatomically shaped to prevent subsidenceand preferably includes projections, ridges, warps or teeth on thesuperior and inferior surfaces for gripping adjacent bone and preventingmigration of the device. The implant also preferably has at least oneopening which accommodates insertion of the device and at least oneopening which accommodates packing of the implant with graft material tofacilitate the formation of a solid fusion structure.

In certain embodiments of the present invention, the implant materialsof the present invention can be comprised of a biocompatible polymericmatrix reinforced or coated with bioactive fillers and fibers. Theimplants can probably be comprised of a diurethane dimethacrylate(DUDMA) and tri-ethylene glycol dimethacrylate (TEGDMA) blended resinand a plurality of fillers and fibers including bioactive fillers andE-glass fibers. The implants may also be comprised of a variety of othermonomers and fillers as described herein.

I. Implant Materials

The present invention provides bioactive and biocompatible implantmaterials for formulation of shaped bodies capable of withstanding largedynamic, compressive loads, especially spinal implants. Further, theimplant materials of the present invention overcome the risks associatedwith disease transmission present with allograft devices. Moreover, theimplant materials of the present invention exhibit a radiopacity similarto that of bone for radiographic assessment of fusion as described inU.S. Pat. No. 6,987,136, issued Jan. 17, 2006, and incorporated hereinby reference in its entirety.

The materials of this invention are preferably comprised of abiocompatible, hardenable polymeric matrix reinforced with bioactive andnon-bioactive fillers. The materials can be comprised of about 10% toabout 90% by weight of the polymeric matrix and about 10% to about 90%by weight of one or more fillers. The materials can also be comprised ofabout 20% to about 50% by weight of the polymeric matrix and about 50%to about 80% by weight of one or more fillers. In order to promote bonebonding to the implants, the implants of the present invention can becomprised of a bioactive material that can comprise a polymeric blendedresin reinforced with bioactive ceramic fillers. Examples of suchbioactive materials can be found, for example, in U.S. Pat. Nos.5,681,872 and 5,914,356 and 6,987,136, which are assigned to theassignee of the present invention and incorporated herein by referencein their entireties.

The polymeric matrixes of the implant materials are comprised ofpolymerizable monomer, monomers, dimers or trimers. They can compriseethylenically unsaturated monomers or even an acrylate functional group.The term “monomers,” as used herein, can also represent dimers, trimers,resins, resin components, or any other polymerizable component. Examplesof the monomers include, but are not limited to, DUDMA,bisphenol-A-glycidyl methacrylate (bis GMA), TEGDMA, ethoxylatedbisphenol-A-dimethacrylate (bis-EMA), or combinations thereof. Still,further examples of monomers that can be used in the present inventioninclude the adducts of 2,2,3-trimethylhexane diisocyanate withhydroxyethyl methacrylate, hydroxypropyl methacrylate, and otherhydroxyacrylic acrylic species can also be used. Other examples ofpolymerizable species that can be used in the present invention includethose disclosed in U.S. Pat. Nos. 5,681,872 and 5,914,356, and6,987,136, which are incorporated herein by reference in theirentireties.

Methyl methacrylate, ethyl methacrylate, propyl methacrylate, highermethacrylates, acrylates, ethacrylates, and similar species can beemployed as all or part of the polymerizable materials of the implantmaterials of the present invention. It is also possible to employ othertypes of polymerizable material such as epoxide compounds,polyurethane-precursor species, and a wide host of other materials. Forexample, other monomers useful in the production of hardenablecompositions of this invention include methyl-, ethyl, isopropyl-,tertbutyloctyl-, dodecyl-, cyclohexyl-, chloromethyl-,tetrachloroethyl-, perfluorooctyl-, hydroxyethyl-, hydroxypropyl-,hydroxybutyl-, 3-hydroxyphenyl-, 4-hydroxphenyl-, aminoethyl-,aminophenyl-, thiophenyl-, acrylate, methacrylate, ethacrylate,propacrylate, butacrylate, and chloromethacrylate, as well as thehomologous mono-acrylic acid esters of bisphenol-A, dihydroxydiphenylsulfone, dihydroxydiphenyl ether, dihydroxybiphenyl, dihydroxydiphenylsulfoxide, and 2,2bis(4-hydroxy-2,3,5,6-tetrafluorophenyl)propane.Polymerizable monomers capable of sustaining a polymerization reactionsuch as the di-, tri-, and higher acrylic ethylene glycoldimethacrylate, diethylene glycol dimethacrylate, trimethylene glycoldimethacrylate, trimethylol propane trimethacrylate, analogousacrylates, and similar species are also useful. Polyetheretherketone(PEEK), carbon fiber reinforced PEEK, and carbon fiber reinforced bariumsulfate impregnated Peek may also be used. Other polymers that may beused include polyethlene and polylactic acid (PLA). PLA may be used withpteroylgutamic acid (PGA) or PGA may be used without PLA. Poly-L-lacticacid (PLLA) may also be used. It is also possible to employ mixtures ofmore than two polymerizable species to good effect.

The implant materials can also comprise non-bioactive substances.Titanium, stainless steel, and cobalt chromium may also be used in thesubstances that comprise the spinal implant.

The implant materials of the present invention can further comprisepolymeric additives that include, but are not limited to, polymerizationinhibitors, polymerization activators, polymerization initiators,stabilizers such as UV-9, radiopacifiers, reinforcing components (i.e.,fibers, particles, micro spheres, flakes, etc.), bioactive fillers,neutralizing resins, diluting resins, antibiotic agents, coloringagents, plasticizers, coupling agents, free radical generators,radiographic contrast agents, and antibiotics.

In many embodiments, the implant materials include a blended resin ofDUDMA to impart strength, TEGDMA to impart flexibility, a benzoylperoxide initiator (BPO) or any peroxide initiator that is consumedduring the polymelization reaction, and at least one polymer stabilizer.The implant materials can also include a plurality of fillers andfibers. The fillers can be of the combeite type, such as the combeitefiller described in U.S. Pat. Nos. 5,681,872 and 5,914,356, incorporatedherein by reference in their entireties, to render the materialbioactive and encourage direct bone bonding. Alternatively, the fillercan be selected from a group of fillers including, but not limited to,borosilicate, silica, Wollastonite, hydroxyapatite (HA), beta-tricalciumphosphate, calcium sulfate, alumina, and the like. In embodiments wherethe implants further comprise fibers, the fibers can further includeE-glass fibers of the composition type [SiO₂ CaO Al₂O₃ B₂O₃], A-glassfibers, silica, or a plurality of other fibers including but not limitedto Kevlar and carbon fibers for imparting toughness and strength to theimplant. In certain embodiments, the fillers and fibers are surfacetreated for incorporation and bonding between them and the resin. Forexample, the fillers and fibers can be silanated, silicone-oil treated,or provided with coupling agents such alumina, titania, or zirconiacoupling agents.

In one embodiment of the present invention, the monomers, fillers, andother additives are blended together to form a paste composition. Thepaste compositions are easily mixed via a low speed, high shear rotarymixer. The duration of the blending operation will vary depending uponthe constituents that comprise the paste composition precursors. In oneembodiment, the blending of the monomers and other additives within thepaste composition precursors activates the polymerization of thecomposition. In another embodiment, exposure to heat either during orafter blending activates the polymerization. The exposure can occur intemperature ranges of about 40° C. to about 180° C. or about 60° C. toabout 120° C. in some instances.

The implant materials of the present invention can be comprised of aone-paste system or combined with two or more paste compositions to forma multiple paste system. Depending upon whether the implant material isa one paste or multiple paste system determines the hardening of thematerial. The paste compositions of the present invention can behardened by thermal energy, photochemical energy, and treatment bychemical process. One skilled in the art may also choose to do so in acontrolled fashion. In certain embodiments wherein the implant materialscomprise a one-paste system, the paste composition is hardened or curedvia exposure to heat or light. Alternatively, the paste compositioncould be cured via gamma radiation. In some embodiments, additionalexposure to gamma radiation can impart additional strength. In otherembodiments wherein the implant materials comprise a multiple pastesystem, the paste compositions are admixed and hardened via thermalenergy or heat cured. The paste compositions can also be chemicallycured via catalyst or redox systems. It will be understood, however,that a wide variety of polymerization systems and materials for usetherein can be employed to good advantage in connection with the presentinvention and all such systems are contemplated hereby. Depending uponthe system that is employed, the paste composition can generallycomprise heat-culling catalysts, photopolymerization, or redox (i.e.N,N(dihydroxyethyl)-p-toluidine(DHEPT), BPO, Fe(II), tertiary butylhydro-peroxide (t-BHP)) initiators. Polymerization materials andcatalytic systems known in the art and not inconsistent with the objectsof this invention can be employed.

In multiple paste systems where heat curing is used to harden thecomposition, a catalytic system is employed such that when twocomponents of the hardenable composition are mixed together, thecatalytic action begins, leading to hardening. This system is familiarand can be applied to a wide variety of polymerizable species includingmany which are suitable in the present invention. Radical initiatorssuch as peroxides, especially benzoyl peroxide (also called dibenzoylperoxide) are conventional, economic, and convenient. A stabilizer suchas butyl hydroxy toluene is customary, as is employment of co-catalystslike dimethyl-p-toluidine, N-N-substituted toluidine, and otherconventional catalysts including tertiary amine structures with doublebond functionality like diethyl aminoethyl methacrylate andN,N-dimethyl-p-toluidine. In general, one of the pastes incorporatesboth the radical initiator and stabilizer, such as a peroxide, and theother paste incorporates the accelerator, such as an amine or toluidine.Curing is initiated by an oxidation-reduction mechanism upon mixing thetwo pastes together.

In paste systems where culling via exposure to heat or other means isused to harden the composition, a photoinitiation system can be includedwith the hardenable compositions and the same caused to be activated byexposure to actinic light of a suitable wavelength. Both ultraviolet andvisible photocuring systems are known for use in restorative surgery anddentistry and any such system can be employed herein. Exemplary systemsare described in U.S. Pat. No. 4,110,184 to Dart et al., U.S. Pat. No.4,698,373 to Tateosian et al., U.S. Pat. No. 4,491,453 to Koblitz etal., and U.S. Pat. No. 4,801,528 to Bennett, which are incorporatedherein by reference in their entireties to provide enablement for suchknown systems.

A particularly useful system employs visible light culling, thusavoiding the potential danger inherent in culling with ultravioletradiation. Visible light culling has been well refined in the dentalfield and the same can also be applied to restorations of bony tissues.Quinones, as a class, find wide utility as photochemical initiators forvisible light sensitizing systems, preferably when the same are admixedwith tertiary amines. Some skilled artisans may prefer that an alphadiketone (quinone) such as camphoroquinone or biacetyl be admixed withan amine reducing agent such as n-alkyl dialkanolamine ortrialkanolamine. Other such photo-initiator systems include a2-benzyl-2-(dimethylamino)-4′-morpholinobutyrophenone, or 50%/50% weightcomposition of 2-hydroxyethyl-2-methyl-1-phenyl-1-propanone anddiphenyl(2,4,6-trimethylbenzyl)phosphine oxide. However, other suchcuring systems or combinations of curing systems can also be employedwith the materials of the present invention.

In some embodiments, one or more fillers are blended into the pastecomposition after the monomers and other additives comprising the resinblend have been combined. The fillers are preferably added incrementallyto avoid binding during the blending process. A vacuum may be appliedduring blending to minimize porosity and dusting. In embodimentscomplising multiple fillers, such as E-glass fibers, borosilicatefillers, silica fillers, and combeite fillers, the E-glass fibers may beadded first followed by the remaining fillers in a designated order.Alternatively, one or more fillers may be pre-blended together prior toincorporation into the resin blend. After the filler has been combinedwith the resin mixture, the completed paste mixture may be agitated viaa vibrating table, ultrasonic, or similar means for a period of timeranging from about 5 minutes to about 60 minutes to further reduceporosity. A vacuum may be applied during the agitation step.

Although the uses described above are exemplary for the presentinvention, there are other embodiments that may be foreseen by thoseskilled in the art. Within the dental field, the implants of the presentinvention can have use as dental crowns (temporary or crown) and dentalimplants, including Maryland bridges. The implant materials can alsohave use as implants for other areas of the animal body. Suchforeseeable implants include cochlear, cranial, tumor, sternum, or othercustom implants that can be MRI compatible or functional shapes made forthe body. Other embodiments can be used for formulation of universalplates for orthopedic use, bone screws, rods, and pins for orthopedicuse (IM nails, femoral rods or plugs, long bone fractures, etc.), tendonanchors, suture anchors and tacks, graft retainers, and marrow samplingports.

Other uses include non-articulating artificial joint surfaces, sensoranchors or housings, bone spacers or wedges (tibial, femoral), cartilagebeds or anchors, or drug delivery. It is also foreseeable that theimplant materials can be used in methods for repairing the iliac harvestsite. The materials can be incorporated into drug delivery beads intobone or in interbody balls. There can also be applications formandibular joints (TMJ) and orbital reconstruction.

One embodiment of the present invention involves machining of theimplantable materials into morsels for use in methods to treat segmentaldefects. The morsels can also be used for minimally invasive loadbearing applications. The material can be made into a mesh forpostero-lateral fusion or cages for other materials. Other embodimentsinvolve the material being used as a cannulated screw with peripheralholes used in methods for treating vertebral augmentation. The presentinvention can have embodiments involving synthetic bones.

II. Cervical Implant

The bioactive implant material may be formed into a variety of shapesfor use as spinal implantation or spinal fixation devices. In oneembodiment, the implant material is preferably formed into a cervicalimplant device. While the present invention is described in terms of theimplant material of the present invention, it is understood that othermaterials may be used to form the cervical implant of the presentinvention.

FIGS. 1 through 4 illustrate various aspects of one embodiment of thecervical implant 10 of the present invention. Implant 10 may vary issize to accommodate differences in the patient's anatomy. The implant 10is comprised of an anterior side 60, a posterior side 70 opposing theanterior side 60, and a pair of opposing sidewalls 40. The anterior side60, the posterior side 70, and the sidewalls 40 are generally outwardlycurved in transverse cross-section. The curved sides are convex asviewed from the outside of the implant 10. The anterior side 60, theposterior side 70, and the sidewalls 40 join at points that generallydefine, in transverse cross section, a trapezoid. The transversecross-section, as used herein, is the plane perpendicular to the z-axis.As used herein, a trapezoid is a quadrilateral having two parallelsides, or any shape having the form of a trapezoid. The presentinvention employs geometric shapes to illustrate a preferred embodiment,but the present invention is not limited to such shape. Rather, thepresent invention broadly encompasses any variation in the claimedshapes within the spirit of the disclosure, including (for example)configurations in which gradually merge with adjacent sides andnon-uniform shapes that vary according to the transverse or longitudinalcross section.

The implant also comprises a top surface 20 and a bottom surface 30 thatis generally opposite the top surface 20. The top 20 and bottom surfaces30 can also be convex, or outwardly curved, in the longitudinalcross-section. The curvature and shape of each side grants the implantsuperior anatomical compatibility. The surfaces also maximize contactwith cortical bone to minimize subsidence of the implant into theendplates.

The top 20 and bottom 30 surfaces further include a plurality ofprojections 25, preferably wave-like or scalloped in shape (i.e.,pointed apex with rounded valleys), for gripping adjacent vertebrae. Thescalloped shape tooth design eliminates the stress concentrationtypically associated with other tooth designs and more evenlydistributes the compressive physiologic loads from the bone to theimplant. The projections 25 can be substantially uniform, upwardlyprotruding ribs. One skilled in the art would recognize theseprojections 25 as being substantially uniform, upwardly protruding,elongated ribs separated by concave channels. In alternativeembodiments, the projections are randomly disposed or, in other words,situated in various directions. These projections 25 may also beupwardly protruding spikes. The wave-like shape of the projections 25increases the surface area of the implant for maximal vertebral contact.Further, the wave-like projections 25 provide significant resistance toexpulsion and retropulsion. In certain preferred embodiments, theprojections 25 have an angular pitch of between 1.75 degrees to 1.9degrees, a minimum depth of 0.022 inches, and an internal radius ofabout 0.022 inches. Other dimensional sizes of the projections 25 wouldnot depart from the present invention including upwardly protrudingspikes.

FIGS. 3 a and 3 b illustrate two alternative embodiments of the presentinvention. FIG. 3 a illustrates implant 10 wherein the wall of theanterior 60 side has greater height than the wall of the posterior 70side. The implant 10 of FIG. 3 a has a lordotic angle. FIG. 3 billustrates implant 10 having no lordotic angle wherein the height ofthe wall for the anterior 60 side is equal to the wall height of theposterior 70 side. Due to the variety of machinations that may be usedto make the implants of the present invention, minute variations mayexist in the height of the anterior 60 and posterior sides that wouldnot render them exactly the same height. Preferable lordotic angles fallin the range of about −20 degrees to about +20 degrees.

In FIG. 4, the implant 10 has a trapezoidal shape defined by thesidewalls 40, anterior 60, and posterior 70 sides. This shape maximizescontact with cortical bone. In preferred embodiments, the top 20 andbottom 30 surfaces are substantially identical in size and shape. Theshape also allows one skilled in the art to place graft material withina major recess 35 bordered by the sidewalls 40, anterior 60, andposterior sides. This major recess 35 is formed in the body and is incommunication with at least one of the top or bottom surfaces. Apreferred embodiment has the major recess 35 having a through-aperturethat is in communication with both top 20 and bottom 30 surfaces.

The implant also has a handling feature that may comprise at least onepair of elongated side recesses 43 and 53 for receiving forceps and afront recess 63 for receiving an impaction tool. The front recess 63 maybe used in conjunction with the anterior side 60 and front opening 65 asto communicate with an implant holder or insertion tool. The frontrecess 63 may be elongated with a major axis that is substantiallytransverse. The front recess 63 may have an aperture, the front opening65, formed therein. This handling feature allows for handling andinsertion of the spinal implant using instruments such as forceps. Insome embodiments, the handling feature consists of only the front recess63. In FIGS. 1 through 3, the sidewalls 40 further comprise siderecesses 43 and 53 that may mate with an instrument to aid in insertionor removal of the implant. The sidewalls 40 also comprise at least oneopening 45 (FIGS. 1 and 3) to allow fluid to enter the major recess 35after insertion. Graft material may be supplied with blood and otherbiologic fluids through the openings 45. In other embodiments, thehandling feature consists of only the side recesses 43 and 53. Thesurfaces of these recesses may be textured with an anti-skid material toprevent slippage of the insertion tool.

In FIGS. 1 and 2, the front recess is used to prevent rotation of theimplant. The front recess 63 and a front opening 65 can mate with animplant insertion tool. The front recess 63 may be comprised of someother geometry suitable to prevent the implant from rotating on the endof the implant insertion tool during insertion or removal of theimplant. In certain embodiments, the front opening 65 may be threaded tomate with a corresponding implant insertion tool. In other embodiments,the front recess 63 is eliminated.

FIG. 5 provides an exploded view of the implant 10 showing graftmaterial 80 being placed in the major recess 35. Graft material may becomprised of allograft material, autograft material, or syntheticmaterials that have similar properties to allograft or autograftmaterials. The synthetic graft material is preferably comprised of abiocompatible, osteoconductive, osteoinductive, or osteogenic materialto facilitate the formation of a solid fusion column within thepatient's spine. One such example of such a synthetic graft material isVITOSS® Synthetic Cancellous Bone Void Filler material, which ismanufactured by Orthovita, Inc. of Malvern, Pa. To foster bone fusion,the VITOSS® calcium phosphate material may be saturated with thepatient's own bone marrow aspirate, or therapeutic material such asgrowth factor, proteins, bone marrow aspirate and other materials suchas those disclosed in U.S. Pat. No. 7,045,125, issued May 16, 2006,incorporated herein by reference. It should be noted that in preferredembodiments, the posterior side 70 does not have an openingtherethrough. This facet of the design is a safety feature implementedto prevent leakage of graft materials placed in the major recess 35 intothe spinal canal.

FIGS. 6 through 8 show a plate 90 and fastener 100 assembly that may beused in conjunction with implant 10. The plate and fastener assembly mayfacilitate fusion of adjacent vertebrae by stabilizing the implant inplace between the vertebrae. Fasteners 100 may be comprised of screws,pins, nails, and the like. They are inserted into openings within plate90 to engage the adjoining vertebral bodies. Upon insertion, one pair offasteners is inserted in the upper vertebral body and one pair isinserted in the lower vertebral body.

FIGS. 9 through 11 show accessories 110 and 120 that are used to connectone or more implants 10 as shown in FIG. 11. Accessories 110 and 120 maybe used in corpectomy procedures in which the surgeon removes one ormore vertebrae and needs to restore the spine to its former height. InFIG. 9, accessory 110 has two male ends that may engage, for example,the major recess 35 of implant 10 or the female end of accessory 120. InFIG. 10, accessory 120 has a male end 123 and a female end that allowsimplants to be joined together as shown in FIG. 11. Accessories 110 and120 may be joined together with implants 10 via snap or compression fitvia one or more flexible tabs, fasteners, adhesives, or other means.

III. ALIF Implant

The bioactive material of the present invention may also be formed intoan implant suitable for ALIF procedures. ALIF implant devices aregenerally suitable for implantation in the lumbar regions of the spine.

FIGS. 12 through 14 depict one embodiment of the ALIF implant 130 of thepresent invention. Like the cervical implant of the present invention,implant 130 may be in a variety of different sizes to accommodatedifferences in the patient's anatomy or the location of the spine thatimplant 130 will be inserted. The body may substantially form an ovalshape in the longitudinal cross-section. The implant is a bodycomprising a bioactive substance and further comprising: an anteriorside 180, a posterior side 190 opposing the anterior side 180, and apair of opposing sidewalls 160, said sidewalls 160 being generallyoutwardly curved or generally “c-shaped.” The anterior 180 and posterior190 sides may be parallel and in others they are outwardly curved. Theimplant also has a top surface 140 and a bottom surface 150, bothsurfaces coupled with the sidewalls 160. Top surface 140 and the bottomsurface 150 form plural projections 145 for enhancing interaction with asynthetic or natural vertebral body. At least one major recess 135 isformed in the body in communication with at least one of the top surface140 and the bottom surface 150.

Also in FIGS. 12 and 14, top 140 and bottom 150 surfaces further includea plurality of projections 145, preferably wave-like or scalloped inshape, for gripping adjacent vertebrae. These projections share the samecharacteristics of the plurality of projections 25 noted in thedescription of the cervical implant.

FIG. 14 illustrates one embodiment of the present invention. FIG. 14illustrates implant 130 having a lordotic angle: The lordotic angle canrange from −20 degrees to +20 degrees.

Similar to the cervical implant 10, the ALIF implant has a major recess135 that forms a through-aperture. This shape maximizes contact with thecortical bone in the thoracic and lumbar regions. In preferredembodiments, the top 140 and bottom 150 surfaces are substantiallyidentical in size and shape. The major recess 135 also maximizes thechances of fusion because graft or resorbable material may be packedwithin implant 10. It should be noted that in preferred embodiments,posterior side 190 does not have an opening therethrough. This is toprevent leakage of graft materials from the major recess 135 into thespinal canal.

The implant also has a handling feature comprising recesses 147 and 157along the top 140 and bottom 150 surfaces extending from either theanterior 180 and posterior 190 sides that act as guide rails and atleast one recess 185 in the anterior or sidewalls 160 for receiving animpaction tool. FIGS. 12 and 13 show the recesses 147 and 157 that actas guide rails. The guide rails mate with an instrument, such as aparallel distraction instrument, to aid in insertion or removal of theimplant. The plurality of guide rails holds the implant securely and mayallow the surgeon to insert the implant more evenly.

FIG. 12, shows the implant 130 having a front recess 183 used as ananti-rotation recess and a front opening 185. The front recess 183 andopening 185 share the same characteristics as the front recess 63 andfront opening 65 of the cervical implant described earlier.

FIG. 15 provides an isometric view of an alternative embodiment 200 ofthe ALIF implant of the present invention. Implant 200 includes a strut210 that divides the major recess 135 into two through-apertures toprovide support during anterior impaction of the implant duringinsertion. A strut 210 that has the top 140 and bottom 150 surfaces withprojections 145 separates the through-apertures.

FIGS. 16 through 19 provides yet another embodiment of the presentinvention in which an ALIF implant 215 or implant 200 further includes afastening feature. The fastening feature comprises at least onethrough-aperture 220 in communication with the anterior 180 side andeither the top 140 or bottom 150 surface for insertion of fasteners 230that communicate with a synthetic or natural vertebral body either belowor above the implant. This feature includes a plurality of openings 220on the anterior side of implant 200 for receiving fasteners 230.Fasteners 230 may include, but are not limited to, screws, pins, nails,or any other fixation devices. In certain preferred embodiments,openings 220 are angled to allow fasteners 230 to move at varying anglesup and in or down and in. An angle in some embodiments that may bepreferred is below about 90 degrees. In others, and angle of about 45degrees may be preferred. Fasteners 230 help to anchor implant 215 sincethe upward tilted fastener is inserted into the upper vertebral body andthe downward tilted fastener is inserted into the lower vertebral body.

IV. PLIF Implant

The bioactive material of the present invention may also be formed intoan implant suitable as for PLIF procedures. PLIF implant devices aregenerally suitable for implantation in the lumbar regions of the spine.

The PLIF implant 240 of the present invention may be in a variety ofdifferent sizes to accommodate differences in the patient's anatomy orthe location in the spine. As FIGS. 20 through 22 illustrate, implant240 comprises an anterior side 290 and a posterior side 300 beingparallel to and opposing the anterior side 290; a medial 280 side and alateral 270 side with one side being outwardly curved and the otherbeing inwardly curved; and a top surface 250 and a bottom surface 260,each of the top 250 and bottom surfaces 260 including plural projections255 for enhancing interaction with a synthetic or natural vertebralbody. The projections 255 are similar in geometry to the protrusions inthe cervical and ALIF implants of the present invention.

The implant also comprises a major recess 245 formed in the bodycreating a longitudinal through-aperture in communication with the top250 and bottom 260 surfaces, at least one minor recess 275 formed in thebody creating a latitudinal through-aperture in communication with themedial 280 and lateral 270 sides, both through apertures incommunication with each other. The convergence of thesethrough-apertures forms a cavity inside the implant in which graftmaterial may be placed. This cavity formed by the through-aperturespromotes bone growth and fusion between the adjoining vertebral bodies.Opening 245 may be packed with graft material to promote bone growth andfusion. Graft materials suitable for this purpose includes any of thematerials disclosed herein. Blood and other biological fluids can beprovided to the graft material through the minor recess 275.

The implant also comprises a handling feature comprising a pair ofanterior recesses 273 formed at points where the anterior 290 sidecommunicates with the medial 280 and lateral 270 sides. The anteriorrecesses 273 are used for receiving a manipulator. There are also a pairof posterior recess 283 formed at points where the posterior 300 sidecommunicates with the medial 280 and lateral sides. The handling featurealso includes a front opening 295 formed in the anterior 290 side. Thehandling feature facilitates the handling and insertion of the spinalimplant into an intervertebral space.

FIGS. 20 and 22 illustrate implant 240 having a lordotic angle. Thelordotic angle can range from −20 degrees to +20 degrees. In otherembodiments, anterior side 300 and posterior side 290 are of the sameheight and have no lordotic angle.

In FIGS. 20 through 22, the anterior recesses 273 and the posterior 283recesses may mate with an instrument, such as forceps, to add in theinsertion or removal of the implant. The front 295 and rear openings 305also allow implant 280 to be gripped and mated with an insertion tool.In certain embodiments, the medial 270 and lateral 280 sides may furthercomprise at least one minor recess 275 (or 285) to allow fluid to enterthe interior of the implant after insertion.

Implant 240 may further include an opening 295 in posterior side 300,that is preferably internally threaded to accommodate an insertion tool,but that does not completely extend through the thickness of theposterior wall. This facet of the design is a safety feature implementedto prevent leakage of graft materials and the like, that may be placedin the hollow interior of the implant, into the spinal canal.

Implant 240 may be used alone or in conjunction with a complimentaryimplant. The two implants can be placed alongside one another as in amirror image with the lateral 270 sides facing one another. Thisconfiguration allows bone graft material to be placed between twoimplants 240 and provides for maximum contact between natural bone andthe implants.

V. TLIF

The bioactive material of the present invention may also be formed intoan implant (FIGS. 22A-22D) suitable for TLIF procedures. TLIF implantdevices are generally suitable for implantation in the lumbar regions ofthe spine.

In another embodiment of the present invention, the TLIF implant x1 ofthe present invention may be in a variety of different sizes toaccommodate differences in patient's anatomy or the location of thespine that the implant x1 will be inserted. The TLIF implant x1 may be avariety of different sizes to accommodate differences in the patient'sanatomy or the location in the spine. As FIGS. 20 through 22 illustrate,implant x1 comprises an anterior side x6 and a posterior side x7 beingparallel to and opposing the anterior side x6 and a medial x8 side and alateral x9 side with at least one side being outwardly curved. Theimplant also comprises a top surface x2 and a bottom surface x3, each ofthe top x2 and bottom surfaces x3 including plural projections x4 forenhancing interaction with a synthetic or natural vertebral body.Wave-like projections x4 are similar to the cervical, ALIF, and PLIFimplants of the present invention.

Top surface and bottom surface x2 and x3 further define at least onemajor recess x5 to promote bone growth and fusion between the adjoiningvertebral bodies. The major recess x5 creates a longitudinalthrough-aperture in communication with the top x2 and bottom x3surfaces. The major recess x5 may be packed with graft material tofurther promote bone growth and fusion. Graft materials suitable forthis purpose includes any of the materials disclosed herein.

As FIGS. 22A through 22D illustrate, the anterior x6 and posterior x7sides are generally flat and parallel. In certain preferred embodiments,the medial x8 side is outwardly curved and the lateral x9 side isinwardly curved.

The implant also comprises a handling feature comprising a pair ofanterior recesses x11 formed at points where the anterior x6 sidecommunicates with the medial x8 and lateral x9 sides and a pair ofposterior recess x10 formed at points where the posterior x7 sidecommunicates with the medial x8 and lateral x9 sides. The pairs ofrecesses (x10 and x11) may be used for communication with a manipulatoror instrument, such as, forceps. The handling feature also includes afront recess x14 formed in the anterior x6 side and a rear recess formedin the postelior x7 side both communicating with a through-aperture.This through-aperture is also in communication with the cavity formed inthe spinal implant by the longitudinal and latitudinalthrough-apertures. The handling feature facilitates the handling andinsertion of the spinal implant into an intervertebral space.

In certain embodiments, medial x8 and lateral x9 sides may furthercomprise at least one opening x12 and x13 to allow fluid to enter theinterior of the implant after insertion to provide graft material placedin the center of the implant with blood or other biological fluids.FIGS. 22C and 22D show an embodiment of the implant x1 with two sideopenings x12 and x13 per wall. However, it should be understood that theimplant x1 may not have side openings, or may have multiple pinholeopenings along the length.

Implant x1 may further include an opening x14 in both of the anterior x6and posterior x7 sides that may be internally threaded to accommodate aninsertion tool. The front recess x14 may have an internal taper to matewith a tapered insertion instrument.

As shown in FIG. 22D, the top and bottom surfaces x2 and x3 may beoutwardly curved. Further, implant x1 may be wedge shaped such thatthere is a lordotic angle. The lordotic angle may be same as thosedescribed earlier in other embodiments of the invention. In someembodiments the height of the wall of the anterior side x8 is greaterthan the height of the wall of the posterior side x9. Alternatively, theheight of these walls may be equal.

The TLIF implant of the present invention is designed to engage thecortical rim of the vertebrae, the strongest portion of the vertebrae,and, as such, increases biomechanical stability. Additionally, theplacement of this type of implant is generally less invasive and lessdestructive than other procedures, and may be cost effective since onlyone implant is used.

VI. Surgical Instrumentation

The present invention also provides surgical instrumentation to aid inthe insertion, placement, or removal of the implants of the presentinvention.

FIGS. 23 through 27 illustrate various aspects of the paralleldistraction instrument 310 of the present invention. Paralleldistraction instrument 310 is suitable for the insertion of the ALIFimplant of the present invention. The instrument 310 includes a pair ofupper 320 and lower 330 forks that mate with the guide rails of the ALIFimplant. For example, FIGS. 23 and 24 show instrument 310 engagingimplant 130 via upper fork 320 engaging guide rails 147 on the topsurface 140 of implant 130 and lower fork 330 engaging guide rails 157on the bottom surface 150 of implant 130. Once instrument 310 holds theimplant securely in place, the surgeon can insert the implant into theintervertebral space. Upon insertion of the instrument 310 with theimplant, the handle 340 (see FIG. 27) of instrument 310 is depressed toactuate the two pairs of forks 320 and 330 in a parallel manner. In analternate embodiment, a further insertion tool may slide betweeninstrument 310 to place the implant in the intervertebral space.Instrument 310 further includes a scissor hinge and ratchet catch toallow for faster actuation than traditional screw style stops of theprior art and a faster release. Once instrument 310 is actuated, adevice of the type shown in FIGS. 28-32 can pass through forks 320 and330 and screw into opening 185 of the implant.

FIGS. 28 through 31 illustrate various features of an implant insertionand impactor tool 350. The tool 350 may be suitable for the insertion orremoval of the cervical, ALIF, and PLIF implants of the presentinvention. Accordingly, the dimensions of tool 350 may vary dependingupon the implant being inserted. Tool 350 includes a tip 360 that iscomprised of a shock absorbing material that can withstand impact, suchas a RADEL® tip and a sturdy body comprised of a material such as metaland a gripping handle 355. Tip 360 can be modular so that it isremovable from the body of tool 350. Tip 360 has a projection 363 thatmates with the anti-rotation convexity of the implant. The tip 360further includes at least one opening 365, preferably a central openingthat allows a “guide wire” with a threaded tip 370 to advance. Incertain embodiments, threaded tip 370 advances through opening 365 uponrotation of the advancer 380 adjacent to the tool handle 353 (see FIGS.28 and 30). Both the threaded tip 370 and projection 363 on the tool tip360 mate with the threaded opening and anti-rotation convexity of theimplant to allow for insertion or removal of the implant.

FIGS. 32 through 34 illustrate various features of another embodiment ofan insertion and impaction tool 390 of the present invention. Tool 390mates (lushly with the implant face and allows for impaction at theopposite end of the tip. Similar to tool 350, tool 390 has a tip 400that is comprised of a shock absorbing material such as RADEL® and asturdy body 393 which is comprised of a metal and a gripping handle 395.Tip 400 has a projection 403 that mates with the anti-rotation convexityof the implant. Tip 400 may further include at least one opening 405,preferably a central opening, that allows a “guide wire” with a threadedtip to advance.

FIG. 35 illustrates an alternate embodiment of the implant insertion andimpaction tool 410 of FIG. 30 that includes a limiting impaction tip420. Limiting impaction tip 420 has stops 430 that allow the surgeon togauge how far tip 420 and the implant is displaced in the anterior toposterior direction with respect to the vertebral bodies. The height ofstops 430 in a vertical direction may be any height that prevents tool410 from going in-between adjacent vertebral bodies. The limitingimpaction tip 420 may be modular or removable from tool 410. Tip 420 maybe made with a set stop length that ranges between about 2 mm to about 4mm to allow the surgeon to gauge how far into the intervertebral spacethe implant is being inserted.

FIGS. 36 through 39 illustrate various aspects of forceps 440 of thepresent invention that may be used for insertion of implants, such asthe cervical implants 10 of the present invention. Forceps 440 may beused to as an alternative to the insertion and impaction tools 350 and390 of the present invention. Forceps 440 are generally scissor-like inshape and have two openings at the handle to accommodate the fingers ofthe surgeon. Forceps 440 may include nubs 450 on the inside of each tip445 for mating with the openings on the medial and lateral sides 43 and45 and 53 and 55 of the implant 10. Tip 445 may further include shockabsorbing pads 460 that are comprised of a material such as RADEL® tocushion the implant if the forceps 440 are also used for impaction.

FIGS. 40 and 41 provide an exploded and isometric view of an insertionand impaction tool 470 that is suitable for use with any of the implantsof the present invention. Tool 470 may be provided with a modular tip480 that may be made of a shock absorbing material, such as but notlimited to RADEL®, that is secured to tool 470 with a fastener 490 orother means. This allows tip 480 to be replaced after wear due torepeated use. Alternatively, the insertion and impaction tool may beintegral with the tool body and handle such as tool 500 in FIG. 42.Preferably the tip of tool 470 or 500 is rounded and smooth-edged. Inuse, the impactor and insertion tool 500 is placed flush against theimplant 10 (see FIG. 43) and then tapped via impaction hammer 510 toadjust the position of the implant (see FIGS. 44 through 47 c). Theimpaction and insertion tool allows for the surgeon to focus on variouscontact spots such as the medial aspect, the lateral aspect or thecenter of the implant for medial, lateral, and the anterior to posteriorpositioning of the implant (see FIGS. 45 through 47 c).

FIG. 470 shows a side view of a rasp y1 of the present invention used inthe preparation of the endplate. The rasp y1 is in the shape of theimplant being inserted so as to contour the endplates to accommodate theeventual implant being inserted and provide for good contact between theendplate bone and the implant. Although FIG. 470 shows a rasp y1 with aheadpiece y2 in the shape of a cervical type implant, it should beunderstood that the headpiece y2 of the rasp y1 could be in any implantshape including the ALIF, PLIF and TLIF types disclosed herein. Rasp y1also includes a handle y3, which may be integral to or a modular withthe headpiece y2, for gripping and manipulating the rasp y1. FIGS. 48and 49 provide an isometric and detailed isometric view of trial tools520 with plugs 530 of the present invention. Tool 520 is used afterpreparation of the intervertebral space and prior to insertion of theimplant to determine the size of the implant to insert. Plugs 530 can bemodular (i.e., fasten or snap onto the end of tool 520) or be integratedinto tool 520. Plugs 530 are generally the same size and shape of theimplant. In FIG. 49, plug 530 may be similar in size and shape to thecervical implant 10 of the present invention.

FIGS. 50 through 52 illustrate various aspects of the view of graftimpaction block and implant/tool holder 540 of the present invention.Graft impact block 540 comprises a plurality of recesses 550 of varioussizes to accommodate various sizes of implants of the present invention.Block 540 allows the graft material to be packed into the hollowinterior of the implant.

EXAMPLES Example 1 Bioactive Spinal Implant Material

An exemplary implant material for the manufacture of spinal implants inaccordance with the invention was formulated to exhibit biocompatibilityand bioactivity for bone bonding, radiopacity similar to bone in orderto be able to assess fusion, mechanical strength to support physiologicloads, and bone-like stiffness to allow for good load sharing among theelements of the spine.

One implant material includes a polymeric blended resin, comprising 20%to about 50% by weight of the implant material total composition. Theresin blend can be further comprised of from about 30% to about 90% byweight of resin OUOMA, about 10% to about 0.25% by weight of butyratedhydroxy toluene (BHT).

The remainder of the implant material is comprised of a plurality offillers. The fillers can be further comprised up to about 40% by weightof filler surface treated E-glass® fibers to impart fracture toughnessand mechanical strength. The filler also can have an average length ofabout 3000 μm or less and an average diameter range of about 5 μm to 50μm; about 5% to about 50% by weight of filler surface treated, silanatedcombeite filler having bioactive characteristics which promote bonebonding; up to about 50% by weight of filler of a surface treatedborosilicate glass filler having an average diameter of −10 μm (e.g.,90% of the particles have a diameter of less than 10 μm, measured bylaser analysis); and up to about 30% by weight of filler of a surfacetreated silica for imparting mechanical strength and to act as arheology modifier. In this particular example, the filler is comprisedof about 20% by weight surface treated E-glass® fibers, about 20% byweight of filler surface treated, silanated combeite filler, about 23%by weight of filler of a surface treated borosilicate glass filler, andabout 5% by weight of filler is surface treated silica. Once allcomponents are combined, the formulated material is hardened viaconventional heating processes, which initiates the polymerizationreaction.

Example 2 Radiopacity of a Bioactive Spinal Implant

Quantitative Evaluation: Three tensile bar samples of polymerizedbioactive material of the type described herein, approximately 4 mm inthickness, were arranged onto x-ray film, and a 16-step Aluminum stepwas placed on top. The 10-mm thick Aluminum step was placed so that itwas partly shielding a polymerized sample and partly over x-ray filmonly (these materials were situated in a Faxitron x-ray cabinet). Theuse of an Aluminum background allowed for more reproducible comparisonbetween x-rays than the use of exposed film alone. The other two sampleswere placed at the ends of the wedge in order to balance it.

The lowest stage in the Faxitron cabinet was used and its focus-filmdistance was 50 mm. The 4-mm thick samples were exposed usingappropriate exposure time and voltage (180 sec., 80 kVp). A backgroundoptical density ranging from 0.8 to 1.2 defined an appropriate exposure.

After the film had been exposed to x-rays, it was removed from theFaxitron and developed.

Using the densitometer, Background (B), Sample(S) and Aluminum (A)density values were recorded.

The same process was used to determine the radiopacity values of gammairradiated material as prepared in accordance with Example 1 above.

Calculations

The percent relative linear attenuation coefficient, α, was calculatedas follows:

$\alpha = {\frac{\left( {B - S} \right)}{\left( {B - A} \right)} \times 100}$

where:

-   B=background optical density of 10 mm of Al, in the range of 0.8 to    1.2.-   A=optical density under the 14 mm thickness of Al (4 mm Al sample    added to 10 mm Al background), and-   S=optical density of the image of the 4 mm thick sample.

Results

Quantitatively, the material, before gamma irradiation, had an averageradiopacity value of 45.55.

TABLE 1 Optical density values for three lots of material prior to gammairradiation. Linear Back- Sample, Aluminum, attenuation Lot NumberSample ground, B S A coefficient, a 022601-067 1 0.89 0.76 0.58 41.94 20.86 0.73 0.57 44.83 3 0.92 0.78 0.61 45.16 Mean 0.89 0.76 0.59 43.98S.D. 0.03 0.03 0.02 1.77 022601-074 1 0.92 0.78 0.61 45.16 2 0.83 0.710.55 42.86 3 0.93 0.78 0.60 45.45 Mean 0.89 0.76 0.59 44.49 S.D. 0.060.04 0.03 1.42 032601-082 1 0.92 0.78 0.60 43.75 2 0.91 0.77 0.66 56.003 0.85 0.72 0.56 44.83 Mean 0.89 0.76 0.61 48.19 S.D. 0.04 0.03 0.056.78 022601-067 Mean 0.89 0.76 0.59 43.98 022601-074 Mean 0.89 0.76 0.5944.49 032601-082 Mean 0.89 0.76 0.61 48.19 Mean 0.89 0.76 0.60 45.55S.D. 0.00 0.00 0.01 2.30

Quantitatively, the material, after gamma irradiation, had an averageradiopacity value of 42.94.

TABLE 2 Optical density values for three lots of material after gammairradiation Linear Back- Sample, Aluminum, attenuation Lot Number Sampleground, B S A coefficient, a 022601-067 1 1.01 0.85 0.62 41.03 2 0.990.84 0.63 41.67 3 1.05 0.89 0.68 43.24 Mean 1.02 0.86 0.64 41.98 S.D.0.03 0.03 0.03 1.14 022601-074 1 1.01 0.85 0.64 43.24 2 1.00 0.84 0.6242.11 3 1.01 0.85 0.64 43.24 Mean 1.01 0.85 0.63 42.86 S.D. 0.01 0.010.01 0.66 032601-082 1 0.99 0.84 0.63 41.67 2 0.98 0.83 0.62 41.67 31.01 0.83 0.64 48.65 Mean 0.99 0.83 0.63 43.99 S.D. 0.02 0.01 0.01 4.03022601-067 Mean 1.02 0.86 0.64 41.98 022601-074 Mean 1.01 0.85 0.6342.86 032601-082 Mean 0.99 0.83 0.63 43.99 Mean 1.01 0.85 0.63 42.94S.D. 0.02 0.02 0.01 1.01

Conclusions

A total of three lots of polymerized bioactive material consisting ofthree samples per lot of material was evaluated and compared directly toAluminum for radiopacity determination. All testing was conducted inaccordance with Orthovita's Technical Operating Procedure. Resultssummarized in the preceding tables indicate that the bioactive spinalmaterial has an average radiopacity value of 45.55 before gammairradiation and a radiopacity value of 42.94 after gamma irradiation.Statistical analysis of results demonstrates that there is not asignificant amount of variance between lots and data records, p=0.445for pre-gamma data and p=0.624 for post-gamma data. Statistical analysisalso shows that there is not a significant amount of variance betweenpre and post gamma data. This indicates that gamma irradiation does notsignificantly affect the radiopacity of the material.

Radiopacity of polymerized material for medical use is clinicallyimportant due to the frequency of using x-rays in measuring theplacement, function, form, and effectiveness of the material. Both preand post gamma bioactive implants have a radiopacity value that willallow for good radiographic viewing that will aid in the placement andpostoperative monitoring of spinal implants made from this material.Radiopacity values for the bioactive spinal implant material of thepresent invention compare favorably with human bone, which has aradiopacity range of between 24 to 52.

As observed in FIG. 53 a, the radiopacity of the material of the presentinvention allows for visualization of the implant between adjacentvertebral bodies (in this case in a segment of a sheep spine), as wellas visualization for the eventual assessment of fusion from amedial-lateral radiograph. This observation is also noted in FIGS. 53 band 53 c, in comparison to a titanium implant.

Example 3 Mechanical Properties of a Bioactive Spinal Implant Material

Samples were prepared using the bioactive material described herein.Tests were performed using ASTM Guidelines on an Instron Model 8516 inorder to obtain ranges of values of mechanical properties of thematerial as shown in the table below.

TABLE 3 Mechanical Properties of a Bioactive Spinal Implant MaterialHUMAN CORTICAL TEST RESULT BONE LITERATURE Compressive Strength 220-250MPa 167-215 MPa ASTM F 451-95 and ASTM D695-91 Compressive Modulus7.0-9.0 GPa 14.7-19.7 MPa ASTM F 451-95 and ASTM D695-91 CompressiveYield Strength 170-182 MPa 121-182 MPa ASTM F 451-95 and ASTM D695-91Tensile Strength 65-100 MPa 70-140 MPa ASTM D638-98 Tensile ElasticModulus 14-17 GPa 10.9-14.8 MPa ASTM D638-98 3-Point Flexural Strength100-120 MPa 103-238 MPa ASTM D790-90 Shear by Punch Tool 60-80 MPa 51.6MPa ASTM D732-93 Compressive Fatigue Strength 170-190 MPa >100 MPa (10⁶cycles) Tensile Fatigue Strength 35-55 MPa 49 MPa (10⁶ cycles)

Example 4 Bioactivity Testing of a Spinal Implant

Bioactivity testing was performed on disc shaped implants comprised ofthe material described herein. Bioactivity for this Example was definedas the ability of the implant to form a calcium phosphate layer on itssurface.

Uncured samples of the material described in Example 1 were injectedinto 5 cc syringes. The material was heated at 100° C. for 1 hour forcomplete polymerization. The rods formed within the syringe were cutinto thin disks (approximately 1 mm thick) using a Buehler diamond bladesaw. Simulated body fluid (SBF) was prepared according to the Kokuborecipe (fluid which simulates blood plasma) and using a balance, 250grams of simulated body fluid was weighed into 5 high densitypolyethylene (HDPE) bottles. One disk of material was placed in each ofthe five bottles. The containers of SBF containing the disks were placedat 37° C. for specified intervals. The time intervals were 6, 12, 19,30, and 50 days. A sample size of 1 disk was prepared at each timeperiod. At these time points, one disk of material was removed from itsbottle. The sample was dried with compressed air prior to analysis. TheSBF was not analyzed prior to immersion of samples and was discardedafter the last sample was removed.

As a non-destructive test, Fourier Transform Infrared Spectroscopy(FTIR) was performed first on the samples. The samples were analyzedusing the Nicolet Instruments Magna 560 FTIR. The stage used for thisanalysis was a single-bounce Attenuated Total Reflectance (ATR) with adiamond crystal and KRS-5 lenses. This stage permitted a surfaceanalysis of the composites through the entire mid-infrared spectrum from4000 to 400 cm⁻¹ samples were analyzed at a 4 cm⁻¹ resolution. Thesamples were placed in direct contact with the ATR crystal. Contact wasmaximized via an anvil on the opposite side of the sample. Spectra werecollected on several areas of the composite samples. At each time point,spectra were analyzed for the presence of key calcium phosphate bands ascompared to the Day 0 control. [0158] After FTIR analysis, the samesamples were then used for Scanning Electron Microscopy/EnergyDispersive Spectroscopy (SEM/EDS). Samples were coated with a thin layerof gold-palladium using a Hummer Sputter Coater. Samples were paintedwith a small amount of conductive silver paint, when necessary. Theoperation procedure of the SEM analysis followed the standard procedurefor the operation of the JEOL JSM-840A and the EDS analysis. A few ofthe thin disks were cut exposing the cross-section of the composite. Thecross-sections were embedded in epoxy resin revealing the cut surface.Upon complete curing of the epoxy, samples were polished on the BuehlerEcoMet3. Final polishing consisted of a 1-micron diamond suspension.

The characterization of bioactivity of the polymerized composite surfaceby scanning electron microscopy consisted of the following parameters:appearance of calcium phosphate deposition (white in back-scatteredelectron imaging “BSEI” mode) and thickness of calcium phosphate layer.The characterization of bioactivity of the polymerized composite surfaceby energy dispersive spectroscopy consisted of the following parameters:calcium and phosphorous detection and reduction in sodium levels at abioactive filler.

FTIR Results

The Rhakoss FTIR results are shown in FIG. 54. The displayed resultsshow few spectral changes are observed in the early time periods.However, the Day 50 spectrum demonstrates dramatic changes and is verysimilar to hydroxyapatite. The Day results show the maturity of thecalcium phosphate growing on the material. Note the sharpness of the1014 cm⁻¹ band in Day 50 spectra.

The following table outlines the peaks seen on the material incomparison with hydroxyapatite at Day 50 and the molecular assignments:

TABLE 4 FTIR Peaks of the Material of the Present Invention andHydroxyapatite ABSORBANCE BAND (cm⁻¹) HYDROXY- APATITE RHAKOSS MOLECULARASSIGNMENT — 3292 O—H and hydrogen bonding from residual water on thecomposite — 1632 Olefin stretch from the composite 1092 1075 Threecomponents of the out of phase 1014 1014 stretch of the phosphate ion956 960 — — Possibly an out of phase deformation band of a carbonate ionresulting from residual SBF salt 602 598 A split bending mode of thephosphate 559 556 ion

SEM/EDS Results

Day 0 back-scattered electron (BSE) image of a cross-section of thematerial is illustrated in FIG. 55 (500 x). The material demonstrated acalcium phosphate crystal (CaP) as early as 6 days as confirmed by EDSanalysis. The Day 6 sample showed the growth was limited to a fewbioactive fillers. The Day 19 sample showed little differences from theearlier time period as demonstrated in FIG. 56.

By 50 days, the material exhibited a thick, dense CaP layer. Again, thislayer covered the entire surface of the composite. The CaP crystals weremature with the appearance of stacked plates. The CaP thickness wasmeasured as approximately 10 microns, and was interdigitated intobioactive fillers at the surface of the composite. FIG. 57 illustratesthe CaP crystal on the surface of Rhakoss.

FTIR Conclusions

The early FTIR results showed few spectral changes in the material. Boththe Day 6 and Day 19 samples showed the same type of strong organicabsorptions as seen in the Day 0 sample.

By Day 50, the material exhibited a thick surface coating of calciumphosphate. Spectra taken at various locations on the material showedonly inorganic phosphate absorbencies, and none of the organic bandsseen in the previous samples (Day 0, 6, and 19). The depth ofpenetration for this FTIR technique is 2-microns. This indicates thatthe thickness of the calcium phosphate growth is at least 2-micronsthick.

The Day 50 spectra were compared against several types of calciumphosphates in the User library. The best spectral match for both sampleswas hydroxyapatite. This close match indicates that hydroxyapatite isthe calcium phosphate species growing on the sample surface. The primaryhydroxyapatite band seen occurs around 1014 cm⁻¹. This band demonstratesa more resolved hydroxyapatite shoulder at 955 cm⁻¹, pointing to amature species.

SEM/EDS Conclusions

At the Day 50 time period, the matelial appears to have a larger surfacecoverage of calcium phosphate and a thickness of CaP deposition. Theevaluations of the cross-sectioned samples provided an accuratemeasurement of the CaP thickness. Also, the CaP layer was evaluated forits interdigitation into the composite. Several observations of the CaPmigrating into a bioactive E-glass ceramic filler at the surface werenoted.

Based on the results presented herein, the material of the presentinvention can be described as bioactive.

Example 5 Static Compression and Compression Shear of a Cervical Implant

Static compression was performed on 6 spinal implants of the type shownin FIGS. 1-4 with a 7° lordotic angle. All implants withstood at least8.1 kN of axial load before yielding. In compression-shear testing, theweakest implant type (6 mm extra wide) had a yield of approximately 2.7kN. Note that human cervical endplates fail at 2.0 kN directcompression.

Example 6 Fatigue Test (Compression) of Cervical Implant

Fatigue testing was performed on 6 spinal implants of the type shown inFIGS. 1-4. All implants successfully withstood 5×10⁶ cycles in 37° C.phosphate buffered saline solution at a 5 Hz loading frequency from −50Nto −500N with negligible deformation.

Example 7 Compression Tests of Spinal Implant

An axial compression test was performed on a spinal implant of the typerepresented in FIGS. 12-14 using an Instron 8516 at a crosshead speed of1.5 mm/min. Glass-filled Delrin was used as an interface between theimplant and the steel fixtures. The Delrin was machined to mateapproximately with the angle of the implant design. The implant wasdesigned to include a 5° lordotic angle.

Implant failure occurred at approximately 41 kN (about 9000 lbf),approximately 12 times body weight.

An axial compression test was performed on two spinal implants of thetype represented in FIGS. 12-14 and one spinal implant of the typerepresented in FIGS. 1-4 using an Instron 8516 at a crosshead speed of1.5 mm/min. Polyacetal inserts were machined to match each of theimplant's lordotic angle and/or superior and inferior surface contours(e.g., convex top and bottom surfaces). The two implants of the type inFIGS. 12-14 had a maximum implant height of 10 mm and a 5° lordoticangle. Failure occurred at loads of 31 kN and 48.8 kN (10,960 lbf),respectively. The implant of the type in FIGS. 1-4 had a maximum implantheight of 10 mm and 7° lordotic angle. Failure occurred at a load of14.1 kN (3170 lbf).

Example 8 In Situ Testing of a Spinal Implant Tooth Design Study in FoamBone

Pull-out testing of various implants was performed in order to evaluatevarious teeth profiles. Implants of the type shown in FIG. 12 weremachined to produce three different tooth design groups (n=5 per group):basic (or wave-like), pyramid and oblique as shown in FIGS. 58 a, 58 b,and 58 c, respectively. The basic implant tooth profile was complised ofparallel rows of continuous teeth (or waves) in line with the long axisof the ellipsoid implant footprint. The pyramid implant tooth profilewas comprised of rows of discontinuous pyramid-shaped teeth parallel tothe long axis of the ellipsoidal implant footprint. The oblique implanttooth profile was comprised of rows of discontinuous teeth 45° to thelong axis of the ellipsoid implant footprint.

For testing, each implant from each group was placed between foam bonesquares in an MTS with a preload of 500 N, a value chosen for itsrelevance to the lumbar spine. Pull-out tests were performed at 0.4 mm/sand load-displacement was recorded. The maximum average pull-out loadfor the basic design was approximately 1000 N, for the pyramid designwas approximately 650N and for the oblique design was approximately710N. The basic tooth profile appeared to have the greatest pull-outresistance based on this test-in which the pull was in the AP direction.

Example 9 Biocompatibility of a Spinal Implant

Samples of a bioactive spinal implant material were tested forbiocompatibility using ISO Guidelines 10993-1, Biological evaluation ofmedical devices. Under these guidelines and in compliance with U.S. Foodand Drug Administration's Good Laboratory Practice Regulation, 21 CPR,Part 58, the material was evaluated for cytotoxicity, sensitization,intracutaneous reactivity, acute toxicity, and genotoxicity. All resultswere negative and showed the material to be non-cytotoxic,non-allergenic, a non-irritant, non-toxic, non-mutagenic, andnon-genotoxic. In addition, material exhibits a degree of polymerizationabove 98% and analysis revealed organic leachate less than 0.01 ppm/g ofmonomer elution.

Example 10 In Vivo Implantation of a Spinal Implant

Spinal implants of the type shown in FIGS. 20-22 were implanted in threenon-human primates via an anterior interbody spinal surgical technique.Each animal was positioned supine. A standard anterior approach was thenused to expose the lumbar spine. A midline incision was made from theumbilicus toward the symphysis pubis. Dissection was carried downthrough the skin and subcutaneous tissue to expose the midline raphe,which was then incised to enter the abdomen through a transperitonealapproach. Bowel contents were retracted and packed cephalad to protectthe bowel and maintain position out of the exposed operative field. Atthis point, the posterior peritoneal sheath was incised and the greatvessels noted. The aorta, vena cava and bifurcation of the left andright common iliac vessels were dissected for free mobility overlyingthe spine. Middle sacral artery and venous branch were ligated. Thevessels were retracted with blunt retractors to allow direct approach tothe ventral aspect of the lumbar spine. When the disc space L₅₋₆ wasidentified, a marker probe was placed in position and a lateral x-raywas obtained to confirm the appropriate level of disc. Afterconfirmation of level, the probe was removed and a complete discectomywas performed. The anterior longitudinal ligament was cut away as wellas anterior annulus material. The disc was then removed in total.

The bony endplates were cleaned and penetrated so that there wasvascular blood flow across the endplate. To facilitate placement of theimplants, the disc space was distracted using a distracter instrument.Two bioactive spinal implants of the type shown in FIGS. 20-22 wereplaced into the distracted disc space, and carefully impacted. A calciumphosphate/bone marrow aspirate (BMA) bone graft material was packedaround and between the implants in the disc space.

An interference screw and washer system was placed ventrally to preventhyperextension of the motion segment and subsequent dislodgment ormigration of the implant devices. Following placement, the vessels wereallowed to return to their normal position. The posterior peritonealsheath was then closed with running absorbable suture. The bowel contentwas allowed to go back into position followed by standard closure of theventral abdominal wall, the midline fascia, and the skin withsubcuticular absorbable suture material.

Radiographs were taken immediately postoperative to verify implantplacement and serve as baseline for comparison.

The rate and quality of healing were assessed using radiographs and CTscans taken at 1, 2, 3 and 6 months (FIGS. 59 and 60).

At six months post-operatively, animals were anesthetized (induction byketamine (10-15 mg/kg BW IM), and, at the discretion of the attendingveterinarian, diazepam (10 mg, IM) or acepromazine (1.0 mg/kg, IM) andthen euthanized. Following euthanasia, the lumbar spine was retrieved enbloc and the specimens were photographed and observed grossly.

Immediately after sectioning, the excised spinal specimens wereinspected for successful fusion and structural integrity of each motionsegment. The screw and washer system was removed and the cranialsegments were separated from the caudal segments and the specimensphotographed and observed grossly.

Specimens without sufficient structural integrity for mechanical testingwere immediately prepared for histologic evaluation. Those withsufficient structural integrity were mechanical tested and then preparedfor histological evaluation.

All procedures were performed in accordance with Albany MedicalCollege's Internal Animal Care and Use Committee and Quality AssuranceUnit.

Results

Bridging bone was found around the implants in all cases. In all cases,the non-destructive flexion testing supported the presence of fusion.There were no Rhakoss particulates noted, and there were no signs ofadverse response to the implants. In fact, minimal scar tissue wasobserved.

Example 11 Manufacture of Spinal Implants

A resin blend (about 20% to about 50% of total implant composition) ofurethane dimethacrylate (DUDMA), triethyleneglycol dimethacrylate(TEGDMA), initiator and stabilizer were poured into a Ross planetarymixing system (Hauppauge, N.Y.). The mixer was sealed, mixing wascommenced and a vacuum was applied. After the mixer was turned off andthe vacuum released, one or more fillers (about 15% to about 80% of thetotal implant composition) such as E-glass fibers, borosilicate fillers,silica fillers, and combeite fillers were added. Mixing was commencedand a vacuum was drawn upon the addition of each increment of filler.Once all of the fillers were incorporated into the resin, a vacuum wasdrawn for additional minutes. The mixture was then agitated on avibrating table with vacuum for about 5 minutes to 60 minutes. Thematerial was extruded into a mold cavity for molding into various bulkgeometries.

The mold cavities were heated in a Despatch LFD Series oven and cured atabout 40° C. to about 180° C. for a time duration of about 1 hour to 20hours to form a molded body. Various shaped bodies or implant bodieswere then formed.

The materials can also be hot extruded, injection molded, compressionmolded, or reacted in a mold with a catalyst other than heat.

The cylindrical stock was machined at MedSource (Laconia, N.H.) intospinal implants of the various shapes disclosed herein, having agenerally anatomical shape with convex superior and inferior surfaces,lordotic angles and the like.

Those skilled in the art will appreciate that numerous changes andmodifications may be made to the preferred embodiments of the inventionand that such changes and modifications may be made without departingfrom the spirit of the invention. It is therefore intended that theappended claims cover all such equivalent variations as fall within thetrue spirit and scope of the invention.

1. A spinal implant comprising: a body comprising: an anterior side, aposterior side opposing the anterior side, and a pair of opposing sidewalls; the anterior side, the posterior side, and side walls joining atpoints that generally define, in transverse cross section, a trapezoid;said sides being generally outwardly curved; a top surface and a bottomsurface, each of the top and bottom surfaces including pluralprojections for enhancing interaction with a synthetic or naturalvertebral body; and a handling feature comprising at least one of a pairof elongated side recesses for receiving a manipulator and a frontrecess, the handling feature facilitating handling and insertion of thespinal implant into an intervertebral space.
 2. The spinal implant ofclaim 1 wherein the generally outwardly curved sides are convex asviewed from outside said spinal implant.
 3. The spinal implant of claim1 wherein the body forms a lordotic angle of about −20 degrees to about+20 degrees.
 4. The spinal implant of claim 1 wherein the height of theanterior side is greater than a height of the posterior side.
 5. Thespinal implant of claim 1 wherein the body substantially forms atrapezoidal shape in longitudinal cross-section.
 6. The spinal implantof claim 1 wherein the projections are substantially uniform, upwardlyprotruding ribs.
 7. The spinal implant of claim 1 wherein theprojections are randomly disposed.
 8. A spinal implant comprising: abody comprising a bioactive substance, further comprising: sides thatare generally outwardly curved in transverse cross-section; a topsurface and a bottom surface, both surfaces coupled with the sides, eachone of the top surface and the bottom surface forming plural projectionsfor enhancing interaction with a synthetic or natural vertebral body; amajor recess formed in the body in communication with at least one ofthe top surface and the bottom surface, and a handling featurecomprising at least one of a pair of elongated side recesses forreceiving a manipulator and a front recess, the handling featurefacilitating handling and insertion of the spinal implant into anintervertebral space.
 9. The spinal implant of claim 8 wherein the bodyforms a lordotic angle of about −20 degrees to about +20 degrees. 10.The spinal implant of claim 8 wherein the height of the anterior side isgreater than the height of the posterior side.
 11. The spinal implant ofclaim 8 wherein the body substantially forms a trapezoidal shape inlongitudinal cross-section.
 12. The spinal implant of claim 8 whereinthe projections are substantially uniform, upwardly protruding ribs. 13.A spinal implant comprising: a body comprising a bioactive substance,further comprising: an anterior side, a posterior side opposing theanterior side, and a pair of opposing sidewalls, said sidewalls beinggenerally outwardly curved; a top surface and a bottom surface, bothsurfaces coupled with the sides, each one of the top surface and thebottom surface forming plural projections for enhancing interaction witha synthetic or natural vertebral body; at least one major recess formedin the body in communication with at least one of the top surface andthe bottom surface; a handling feature comprising recesses in the topand bottom surfaces in communication with the anterior and posteriorsides and at least one recess in the anterior or sidewalls for receivingan impaction tool, the handling feature facilitating handling andinsertion of the spinal implant into an intervertebral space; and afastening feature comprising at least one through-aperture incommunication with the anterior side and either the top or bottomsurface for insertion of fasteners that communicate with a synthetic ornatural vertebral body.
 14. The spinal implant of claim 13 wherein theanterior and posterior sides are parallel.
 15. The spinal implant ofclaim 13 wherein the anterior and posterior sides are generallyoutwardly curved.
 16. The spinal implant of claim 13 wherein thelordotic angle ranges from about −20. degrees to about +20 degrees. 17.The spinal implant of claim 13 wherein the height of the anterior sideis greater than a height of the posterior side.
 18. The spinal implantof claim 13 wherein the major recess forms a longitudinalthrough-aperture.